JP2008184499A - Polyimide copolymer, positive type photosensitive resin composition and method for forming pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new precursor of a polyimide copolymer, to provide the polyimide copolymer having excellent solder heat resistance and bent plate folding endurance representing folding endurance and to simultaneously provide a positive type photosensitive resin composition having pattern-forming properties of high resolution and developable with an aqueous solution of an alkali. <P>SOLUTION: The positive type photosensitive resin composition comprises (A) the precursor of the polyimide copolymer having a specific repeating unit (hereinafter based on pts.wt.) and the following (B) to (D): (B) 2-5 pts.wt. of a photosensitizer generating an acid by irradiation of active rays, (C) 15-25 pts.wt. of a cross-linking agent represented by general formula (5) (not shown) and (D) 150-1,900 pts.wt. of an aprotic polar amide solvent represented by formula (2) (not shown). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel polyimide copolymer precursor, a solution thereof, a polyimide copolymer, and a positive photosensitive resin composition containing the polyimide copolymer precursor. The present invention also relates to a pattern forming method using the positive photosensitive resin composition and a circuit material obtained by the forming method. More specifically, the polyimide copolymer having excellent heat resistance, solder heat resistance, migration resistance, and transmittance in the ultraviolet region, and excellent in “folding resistance”, which is one characteristic representing folding resistance, and excellent The present invention also relates to a polyimide copolymer obtained from the positive photosensitive resin composition having similar characteristics.

  Further, the present invention uses any of the polyimide copolymer precursor to the solution, the polyimide copolymer, and a positive photosensitive resin composition containing the polyimide copolymer precursor. Related to the coverlay formed. More specifically, the present invention relates to a coverlay that has high-resolution pattern formation, can be developed with an aqueous alkali solution, and has excellent heat resistance, folding resistance, and flame retardancy after cured. Furthermore, the present invention relates to a flexible printed board using the coverlay.

  Polyimide and polybenzoxazole are excellent in heat resistance, mechanical properties, chemical resistance, electrical insulation, etc., so semiconductor surface protective films, interlayer insulation films on multilayer wiring boards, cover coat films on flexible wiring boards, etc. Is expected to expand into the electric and electronic fields. In particular, photosensitive polyimide and photosensitive polybenzoxazole having the function of a photoresist are materials that are attracting attention because they can greatly shorten the processing steps.

  In recent years, there has been a demand for higher speed and higher capacity of computers and measuring instruments in communication information processing technology, and the signal transmission speed of printed wiring boards used for this has increased, and the lower dielectric constant has been reduced. Requests are also increasing. Further, in consideration of safety during work and influence on the environment, there is an increasing demand for a positive photosensitive resin composition that can be developed with an alkaline aqueous solution.

  Until now, as a method of developing positive photosensitivity, a method of introducing an o-nitrobenzyl group into a polyimide precursor via an ester bond (for example, see Non-Patent Document 1), a polybenzoxazole precursor or a polybenzoxazole A dissolution inhibitor addition method in which naphthoquinonediazide is added to hydroxyimide has been proposed (for example, see Patent Document 1 and Non-Patent Document 1). However, the high solubility of the polyimide precursor in alkaline water is a problem and sufficient resolution cannot be obtained, it is limited to a special structure, and the film thickness of the finally obtained film becomes a problem, The current situation is that there is no practical application yet.

  Various photosensitive polyimide skeletons have been proposed so far. However, the wholly aromatic polyimide precursor reported in Patent Document 2 has problems of solubility in an alkaline developer and poor transmittance in the i-line region. In addition, the polyimide precursor obtained by making the acid dianhydride alicyclic has a problem that the reactivity of the acid dianhydride may not be sufficient, a problem that it is likely to be colored, and a structure of the monomeric acid dianhydride is special. Therefore, there is a problem that it is expensive. All alicyclic polyimide precursors have a problem of poor coating formation, and chain aliphatic polyimides have a problem of poor heat resistance (see, for example, Non-Patent Document 2).

  Accordingly, there is a demand for a polyimide precursor using an inexpensive monomer having moderate alkali solubility, heat resistance, and high transmittance in the i-line region.

  In recent years, with the diversification of electronic devices such as miniaturization and sophistication, demand for flexible wiring boards is increasing. A flexible printed circuit board generally creates a circuit on a flexible printed circuit board in which an electrically insulating film and a metal foil are laminated and integrated with an adhesive as required, and this flexible circuit board is used for circuit protection. Coverlay is coated.

  As the cover lay, polyimide film has been used because heat resistance, folding resistance and insulation are required. As a method of attaching the cover lay, a method of laminating a cover lay having a desired hole on a flexible wiring board on which a circuit pattern is formed by thermal lamination or pressing is common.

  Recently, however, the demand for mounting materials has been higher than ever, and the wiring on flexible printed wiring boards is rapidly becoming finer. The method of aligning in this way has a low yield. However, it is in the limit because it is inferior in workability, and it is difficult to obtain position accuracy or low accuracy.

  Therefore, in order to solve such a problem, a photosensitive insulating resin composition capable of using a photolithography method capable of fine processing has been studied as a photosensitive coverlay. These include a dry film type and a liquid type, both of which are currently in practical use.

  The dry film photosensitive coverlay is a protective film such as polyethylene to prevent dust from adhering to the support film by applying an organic solvent solution of a resin composition containing photosensitive polyimide or polyimide precursor to the support film. Used in a state where films are laminated. While it has the merit of being easy to handle, it is common to use a polymer having an acrylic or methacrylic skeleton having a carboxyl group in order to enable development with an alkaline aqueous solution. There was the fault that it was inferior in flexibility (for example, refer to patent documents 3). In recent years, thinning of the flexible printed wiring board has been demanded, and since a support film is used in the dry film method, there has been a problem that it is difficult to reduce the thickness of the film to 50 μm or less.

  As a liquid type photosensitive cover lay, a photosensitive polyimide precursor imparting photosensitivity to polyimide has been proposed, but an organic solvent such as dimethyl sulfoxide or N-methylpyrrolidone is required in the development process. There was a problem in industrial handling.

  Therefore, solder resists for printed circuit boards have been diverted as photosensitive materials that can be developed with dilute alkaline aqueous solutions. However, since the materials are epoxy-acrylic, their flexibility and heat resistance are not sufficient. (For example, refer to Patent Document 4). In addition to heat resistance, folding resistance and insulation, the resin material used for the flexible printed wiring board coverlay is required to have sufficient flame resistance. However, in the examples reported so far, halogen-containing compounds that have a high possibility of generating dioxins during combustion, such as bromine-containing aromatic compounds, are used for the purpose of expressing flame retardancy, or they are toxic substances. At present, antimony compounds are used.

From the above, it can be said that it is desirable to use a polyamic acid that can be dissolved and developed in an aqueous alkali solution before thermosetting, and that the carboxylic acid that is an alkali-soluble group disappears by ring closure after thermosetting. However, it is difficult for conventional polyamic acids to control the dissolution rate in an alkaline developer, and it is difficult to develop a difference in dissolution rate between an exposed area and an unexposed area. Further, in order to exhibit excellent insulation reliability, a film thickness of 10 μm or more is necessary. However, when conventional polyamic acid is used, the transmittance of active ultraviolet rays is very low at this thickness. there were.
JP-A-5-11451 JP-A-6-161110 JP 2003-167336 A JP 2005-232195 A J. et al. Macromol. Sci. Chem. , A24, 10, 1407, 1987 Edited by Japan Polyimide Study Group, Latest Polyimides-Fundamentals and Applications-Ikuo Imai, Rikio Yokota, NTS Corporation, 2002

  An object of the present invention is to provide a novel polyimide copolymer precursor, and the polyimide copolymer excellent in “fracture resistance”, which is one of the characteristics representing solder heat resistance and folding resistance obtained from the precursor. It is to provide a polymer. Also provided is a positive photosensitive resin composition having high-resolution pattern formation, capable of developing with an alkaline aqueous solution, and having excellent heat resistance, fracture resistance, and flame retardancy after curing. It is also a thing. Furthermore, this invention is providing the coverlay which consists of this polyimide copolymer, and a flexible printed circuit board using the same.

Specifically, the present invention is provided by the following [1] to [17].
[1] A polyimide copolymer precursor comprising the repeating structural units represented by formulas (1a) and (1b).

（式中、ｍとｎは、共重合比（モル％）を表し、ｍ＋ｎ＝１００モル％、７０≦ｍ＜１００、３０≧ｎ＞０である。）

(In the formula, m and n represent a copolymerization ratio (mol%), and m + n = 100 mol%, 70 ≦ m <100, 30 ≧ n> 0.)

[2] The precursor of the polyimide copolymer described in [1] is a norbornanediamine represented by the formula (3), 4,4′-diaminodiphenyl ether, and pyromellitic dianhydride, The polyimide copolymer precursor according to [1], which is obtained by reacting in an aprotic polar amide solvent represented by (2).

（式中Ｒ_１〜Ｒ_３は、炭素数１〜３のアルキル基であり、相互に同一でも異なってもよい。）

(Wherein _R 1 to R ₃ is an alkyl group having 1 to 3 carbon atoms, it may be the same or different from each other.)

[3] The precursor of the polyimide copolymer according to [2], wherein the aprotic polar amide solvent of the formula (2) is N, N-dimethylacetamide.

[4] The precursor of the polyimide copolymer according to any one of [1] to [3], wherein the copolymerization ratio n of the formula (1b) is 10 to 20 mol%.

[5] In the polyimide copolymer precursor according to any one of [1] to [4], the transmittance at 365 nm at a film thickness of 10 μm of the film obtained from the precursor is 10% or more. The precursor of the polyimide copolymer in any one of [1]-[4].

[6] A polyimide copolymer comprising the polyimide copolymer precursor according to any one of [1] to [5] and an aprotic polar amide solvent of the formula (2). Precursor solution.

[7] Each repeating structural unit represented by the formulas (4a) and (4b) obtained by dehydrating imidation of the polyimide copolymer precursor according to any one of [1] to [5] Polyimide copolymer.

（式中、ｍとｎは、上記同一）。

(Wherein, m and n are the same as above).

[8] The polyimide copolymer precursor represented by the formulas (1a) and (1b) contained in the solution is simultaneously removed from the solution of the polyimide copolymer precursor described in [6]. A polyimide copolymer represented by the above formulas (4a) and (4b), which is obtained by dehydrating and imidizing the body.

[9] The polyimide according to any one of [7] or [8], wherein the polyimide copolymer according to any one of [7] or [8] has a fracture resistance test value of at least 30 times. Copolymer.

[10] A positive photosensitive resin composition comprising the following (A) to (D).
(A) 100 parts by weight of the precursor of the polyimide copolymer having each repeating structural unit represented by the above formulas (1a) and (1b) (based on the following parts by weight)
(B) 2 to 5 parts by weight of a photosensitizer that generates an acid upon irradiation with actinic rays (C) 15 to 25 parts by weight of a crosslinking agent represented by the general formula (5) (D) aprotic compound of the above formula (2) 150 to 1900 parts by weight of polar amide solvent

（式中、ｌは１以上の整数を示し、Ｒは１価以上の芳香族基、脂肪族基を示す。）

(In the formula, l represents an integer of 1 or more, and R represents a monovalent aromatic group or aliphatic group.)

[11] The photosensitive resin composition according to [10] is desolvated, and at the same time, each of the repeating structural units represented by the formulas (1a) and (1b) contained in the photosensitive resin composition is included. A polyimide copolymer represented by the above formulas (4a) and (4b), obtained by dehydrating imidation of a polyimide copolymer precursor.

[12] The polyimide copolymer according to [11], wherein the fracture resistance test value is at least 10 times in the polyimide copolymer according to [11].

[13] A step (I) of coating the positive photosensitive resin composition according to [10] on a substrate, and a coating step of drying the substrate coated with the solution at 50 to 160 ° C. II), a step (III) in which the obtained coating film is exposed to active ultraviolet rays through a mask pattern and then heated at 80 to 250 ° C., and an aqueous solution of an alkali metal carbonate is used. A precursor of the polyimide copolymer represented by the above formulas (1a) and (1b) by dissolving only the exposed portion and developing the positive pattern and heat-treating the developed positive pattern. And (V) forming a positive pattern containing a body.

[14] The positive pattern forming method according to [13], wherein the alkali metal carbonate aqueous solution according to [13] is a sodium carbonate aqueous solution.

[15] A circuit material obtained by the method for forming a positive pattern according to any one of [13] or [14].

[16] The polyimide copolymer precursor according to any one of [1] to [5], the polyimide copolymer precursor solution according to [6], and [7] to [9]. Any of the polyimide copolymer according to any one of the above, the positive photosensitive resin composition according to the above [10], or the polyimide copolymer according to any one of the above [11] to [12]. Cover lay characterized by forming.

[17] A flexible printed board using the coverlay according to [16].

  The present invention is a novel polyimide copolymer precursor, and the polyimide copolymer excellent in “fracture resistance”, which is one characteristic of solder heat resistance and folding resistance obtained from the precursor. Can be obtained. Also, it is possible to obtain a positive photosensitive resin composition having a high resolution pattern forming property, which can be developed with an alkaline aqueous solution, and has excellent heat resistance, fracture resistance and flame retardancy after curing. You can also. Furthermore, this invention can also obtain the coverlay which consists of this polyimide copolymer, and a flexible printed circuit board using the same, and is industrially very valuable.

[1. Precursor of polyimide copolymer]
[A. Structure and composition of polyimide copolymer precursor]
The precursor of the polyimide copolymer of the present invention is a copolymer composed of each repeating structural unit represented by the formulas (1a) and (1b). In the formulas (1a) and (1b), m and n represent a copolymerization ratio (mol%), and m + n = 100 mol%, 70 ≦ m <100, 30 ≧ n> 0. n is preferably 10 to 20 mol%, more preferably 20 mol%.

  The precursor of the polyimide copolymer of the present invention is composed of each repeating structural unit represented by the above formulas (1a) and (1b), and its copolymerizability, that is, alternation and ordering are not particularly limited. However, they may be present or may be random copolymerization.

  The precursor of the polyimide copolymer of the present invention is composed of norbornenediamine represented by the above formula (3) and 4,4′-diaminodiphenyl ether as diamine components, and pyromellitic dianhydride as tetracarboxylic dianhydride. It is obtained by using a product.

  In the formulas (1a) and (1b), m and n represent a copolymerization ratio (mol%), which is the amount used of norbornenediamine represented by the formula (3) and 4,4′-diaminodiphenyl ether. By controlling the ratio (molar ratio), the copolymerization ratio can be arbitrarily set within the range of 70 ≦ m <100 and 30 ≧ n> 0.

  Specifically, for example, by using an amount corresponding to 80 mol% of norbornenediamine represented by the formula (3) and an amount corresponding to 20 mol% of 4,4′-diaminodiphenyl ether, the above formula is used. The polyimide copolymer precursor of the present invention having a copolymerization ratio such that m in (1a) is 80 mol% and n in the formula (1b) is 20 mol% is obtained.

[B. Polyimide copolymer precursor raw material NBDA]
A specific example of the norbornenediamine represented by the formula (3) used in the precursor of the polyimide copolymer of the present invention is diaminomethyl-bicyclo [2.2.1] heptane (hereinafter abbreviated as “NBDA”). ). NBDA may be any isomer such as a structural isomer having a different aminomethyl group position, or an optical isomer including an S isomer and an R isomer, and the isomer is contained in any proportion. It may be a mixture.

[C. Modification of polyimide copolymer precursor]
[1] Diamine]
As long as the precursor of the polyimide copolymer of the present invention does not impair the purpose of the present invention, the third component is a fat other than the other alicyclic diamine, aromatic diamine, diaminosiloxane, or the above alicyclic diamine. It is also possible to copolymerize an aromatic diamine or the like. The amount of diamine used as the third component is 30 mol% or less, preferably 10 mol% or less of the total diamine component. Moreover, the diamine used as a 3rd component may be used individually by 1 type or in mixture of 2 or more types. Hereinafter, 1) specifically shows alicyclic diamines and aromatic diamines A) to H), diaminosiloxanes (I), and aliphatic diamines (J) to (K).

  1) Alicyclic diamine; 2,5-diaminomethyl-bicyclo [2,2,2] octane, 2,5-diaminomethyl-7,7-dimethylbicyclo [2,2,1] heptane, 2,5 -Diaminomethyl-7,7-difluorobicyclo [2,2,1] heptane, 2,5-diaminomethyl-7,7,8,8-tetrafluorobicyclo [2,2,2] octane, 2,5- Diaminomethyl-7,7-bis (hexafluoromethyl) bicyclo [2,2,1] heptane, 2,5-diaminomethyl-7-oxabicyclo [2,2,1] heptane, 2,5-diaminomethyl- 7-thiabicyclo [2,2,1] heptane, 2,5-diaminomethyl-7-oxobicyclo [2,2,1] heptane, 2,5-diaminomethyl-7-azabicyclo [2,2,1] heptane , 2, -Diaminomethyl-bicyclo [2,2,2] octane, 2,6-diaminomethyl-7,7-dimethylbicyclo [2,2,1] heptane, 2,6-diaminomethyl-7,7-difluorobicyclo [ 2,2,1] heptane, 2,6-diaminomethyl-7,7,8,8-tetrafluorobicyclo [2,2,2] octane, 2,6-diaminomethyl-7,7-bis (hexafluoro Methyl) bicyclo [2,2,1] heptane, 2,6-diaminomethyl-7-oxybicyclo [2,2,1] heptane, 2,6-diaminomethyl-7-thiobicyclo [2,2,1] heptane 2,6-diaminomethyl-7-oxobicyclo [2,2,1] heptane, 2,6-diaminomethyl-7-iminobicyclo [2,2,1] heptane 2,5-diamino-bicyclo [2 2,1] heptane, 2,5-diamino-bicyclo [2,2,2] octane, 2,5-diamino-7,7-dimethylbicyclo [2,2,1] heptane, 2,5-diamino-7 , 7-difluorobicyclo [2,2,1] heptane, 2,5-diamino-7,7,8,8-tetrafluorobicyclo [2,2,2] octane, 2,5-diamino-7,7- Bis (hexafluoromethyl) bicyclo [2,2,1] heptane, 2,5-diamino-7-oxabicyclo [2,2,1] heptane, 2,5-diamino-7-thiabicyclo [2,2,1 ] Heptane, 2,5-diamino-7-oxobicyclo [2,2,1] heptane, 2,5-diamino-7-azabicyclo [2,2,1] heptane, 2,6-diamino-bicyclo [2, 2,1] heptane, 2,6-dia Mino-bicyclo [2,2,2] octane, 2,6-diamino-7,7-dimethylbicyclo [2,2,1] heptane, 2,6-diamino-7,7-difluorobicyclo [2,2, 1] heptane, 2,6-diamino-7,7,8,8-tetrafluorobicyclo [2,2,2] octane, 2,6-diamino-7,7-bis (hexafluoromethyl) bicyclo [2, 2,1] heptane, 2,6-diamino-7-oxybicyclo [2,2,1] heptane, 2,6-diamino-7-thiobicyclo [2,2,1] heptane, 2,6-diamino-7 -Oxobicyclo [2,2,1] heptane, 2,6-diamino-7-iminobicyclo [2,2,1] heptane1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohex S 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane .

2) Aromatic diamines A) to H), diaminosiloxane (I), aliphatic diamines J) to K)
A) having one benzene ring; p-phenylenediamine, m-phenylenediamine.

  B) having two benzene rings; 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl Sulfide, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,4′- Diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) ) Propane, 2- (3-aminophenyl) -2- ( -Aminophenyl) propane, 2,2-di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1, 1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1- Di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1- Phenylethane.

  C) having three benzene rings; 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α) α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine.

  D) having four benzene rings; 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone Bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3- Aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2 , 2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl Nyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) ) Phenyl] -1,1,1,3,3,3-hexafluoropropane.

  E) having 5 benzene rings; 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α- Dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl Benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, F) 4,4′-bis [4- (4-aminophenoxy) having six benzene rings B) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone.

  G) having an aromatic substituent; 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4- Phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone.

  H) 6,6′-bis (3-aminophenoxy) 3,3,3,3,3′-tetramethyl-1,1′-spirobiindane 6,6′-bis (4-aminophenoxy) having a spirobiindane ring ) 3,3,3, '3,'-tetramethyl-1,1'-spirobiindane.

  A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group can also be used. .

  I) Diaminosiloxane; 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethyl Siloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane.

  J) ethylene glycol diamine; bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2-aminomethoxy) ethyl] ether, bis [2- (2-amino) Ethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether, 1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, Triethylene glycol bis (3-aminopropyl) ether.

  K) methylenediamine; ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1 , 9-Diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane.

[2] Tetracarboxylic dianhydride]
The precursor of the polyimide copolymer of the present invention uses pyromellitic dianhydride as an essential raw material, but other tetracarboxylic dianhydrides are used as a third component within a range that does not impair the purpose of the present invention. May be used. The amount of tetracarboxylic dianhydride other than pyromellitic dianhydride that can be used is 30 mol% or less, preferably 10 mol% or less of the total tetracarboxylic dianhydride component.

  Specific examples of the aromatic tetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 2,2-di (3,4-dicarboxy) phenyl- 1,1,1,3,3,3-hexafluoropropane dianhydride may be mentioned.

  Examples of the aliphatic tetracarboxylic dianhydride include cyclobutane tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4 ′. -Tetracarboxylic dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic dianhydride and the like. These tetracarboxylic dianhydrides can be used alone or in combination of two or more of aromatic and / or aliphatic.

[D. End-capping of polyimide copolymer precursor]
The molecular end of the precursor of the polyimide copolymer of the present invention may be sealed. When the molecular terminal is sealed, as is conventionally known, it is desirable to seal with a group that is not reactive with an amine or dicarboxylic anhydride.

  The amount of the dicarboxylic anhydride used for sealing the molecular ends is 0.001 to 1.0, preferably 0.01 to 0.5 mol, per 1 mol of all diamine compounds. Similarly, the amount of monoamine used for end-capping is 0.001 to 1 mole, preferably 0.01 to 0.5 mole, per mole of total tetracarboxylic dianhydride.

  The method of sealing the molecular terminal of the precursor of the polyimide copolymer of the present invention can be divided into the following two methods. On the other hand, when the diamine compound is excessive and the end is sealed with an aromatic dicarboxylic acid anhydride, the tetracarboxylic dianhydride is less than 0.9 to 1.0 mol per mole of the diamine compound, and the dicarboxylic acid anhydride. Is 0.001 to 1.0 mol. On the other hand, when tetracarboxylic dianhydride is excessive and the terminal is sealed with an aromatic monoamine, the diamine compound is 0.9 to less than 1.0 mol per mole of tetracarboxylic dianhydride, and the aromatic monoamine. Is 0.001 to 1.0 mol.

  Specific examples of dicarboxylic acid anhydrides used for sealing molecular ends include phthalic anhydride, benzophenone dicarboxylic acid anhydride, dicarboxyphenyl ether anhydride, biphenyl dicarboxylic acid anhydride, naphthalenedicarboxylic acid anhydride, and the like. Specific examples of amines include aniline, toluidine, xylidine, aminobiphenyl, naphthylamine, and alkylamine.

[Production of polyimide copolymer precursor]
[A. Control of logarithmic viscosity]
In the production of the polyimide copolymer precursor of the present invention, the molecular weight of the polyimide copolymer precursor to be produced can be adjusted by adjusting the amount ratio of tetracarboxylic dianhydride and diamine compound. The molar ratio of the total diamine compound to the total acid dianhydride is preferably in the range of 0.9 to 1.1. When the molar ratio of the total diamine compound and acid dianhydride is 0.9 to 1.1, the logarithmic viscosity of the resulting polyimide copolymer precursor is 0.5 g in N, N-dimethylacetamide solvent. / Dl at a temperature of 35 ° C. and a value of 0.1 to 3.0 dl / g, preferably 0.4 to 1.5 dl / g.

[B. solvent]
The reaction for obtaining the precursor of the polyimide copolymer of the present invention is preferably carried out in a solvent. Examples of the solvent that can be used here include the following.

  A) Phenol solvents: phenol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5 -Xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol.

  B) Aprotic amide solvents; N, N-dimethylformamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphorotriamide.

  C) Ether solvent; 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, tetrahydrofuran, bis [2- (2-methoxyethoxy) ethyl] ether 1,4-dioxane.

  D) Amine solvents: pyridine, quinoline, isoquinoline, α-picoline, β-picoline, γ-picoline, isophorone, piperidine, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine .

E) Other solvents: dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane, diphenyl sulfone, tetramethylurea, anisole These solvents may be used alone or in combination of two or more. When mixed and used, it is not always necessary to select a combination of solvents that are mutually soluble in an arbitrary ratio, and they may be mixed or non-uniform.

  The aprotic polar amide solvent represented by the formula (2) is particularly preferable as the solvent used in the reaction for obtaining the polyimide copolymer precursor of the present invention.

The aprotic polar amide solvent represented by the formula (2) is, for example, when R ₃ which is a monovalent group in the formula (2) is a methyl group, N, N-dimethylacetamide, N, N-diethyl Acetamide, N, N-dipropylacetamide, N, N-diisopropylacetamide, N-methyl-N-ethylacetamide, N-ethyl-N-propylacetamide, N-methyl-N-propylacetamide and N-methyl-N- The same applies when R ₃ is an ethyl group, a propyl group, or an isopropyl group.

  Among them, N, N-dimethylacetamide (hereinafter abbreviated as DMAc) is most preferable. The aprotic polar amide solvent represented by the formula (2) may be used alone or in combination of two or more, and the mixing ratio in the case of mixing is arbitrary.

  Each of the repeating structural units represented by the above formulas (4a) and (4b) obtained by dehydrating imide of the precursor of the polyimide copolymer by using DMAc as the precursor of the polyimide copolymer of the present invention. The transmittance in the ultraviolet region of polyimide composed of

[C. Polymerization concentration]
The concentration of the reaction performed in the solvent (hereinafter referred to as “polymerization concentration”) is not limited. In the present invention, the polymerization concentration carried out in the solvent is the total diamine used and the total diamine used with respect to the total mass of the total mass of the total solvent used and the total mass of the total diamine and total tetracarboxylic dianhydride used. The ratio of the total mass of the tetracarboxylic dianhydride combined is defined as a value expressed as a percentage. A preferable polymerization concentration is 5 to 40%, more preferably 10 to 30%.

[D. Manufacturing conditions]
All known production methods can be applied to the polyimide copolymer precursor of the present invention without any particular limitation. The most common specific method is obtained by reacting the norbornanediamine of the formula (3), 4,4′-diaminodiphenyl ether and pyromellitic anhydride in the solvent.

  The reaction temperature is preferably from −10 ° C. to 100 ° C., preferably in the range from about the ice-cold temperature to around 50 ° C., and most preferably practically room temperature in terms of implementation. The reaction time varies depending on the type of monomer used, the type of solvent, and the reaction temperature, but it is 1 to 48 hours, preferably about 2 to 3 hours to about 10 to several hours. -10 hours. Furthermore, normal pressure is sufficient as the reaction pressure.

  The order of addition of each of the two essential diamines and pyromellitic dianhydride of the present invention is arbitrary, and the addition method of these raw materials can be either batch or divided. In addition, if two or more diamine isomer mixtures having different NBDA isomer composition ratios are used, a polymer having a locally biased diamine composition can be produced even by random copolymerization.

[Characteristics of polyimide copolymer precursor]
The precursor of the polyimide copolymer of the present invention preferably has a transmittance of 10% or more at 365 nm when the film thickness of the film is 10 μm in the film of the precursor obtained therefrom.

  When the polyimide copolymer precursor of the present invention is applied to a photosensitive coverlay, a film thickness of at least 10 μm is required as a film thickness for exhibiting excellent insulation reliability, and the thickness is 10 μm or more. The transmittance of the polyimide copolymer precursor film in the ultraviolet-visible region is important. In particular, the transmittance at 365 nm which is an actinic ray wavelength is extremely important.

  It is preferable that m is within the above range because the transmittance of the coating film at the above film thickness is good. In addition, when the transmittance is less than 10%, the actinic ray is absorbed by the polyimide copolymer film, so that the photosensitive agent is difficult to act and sufficient irradiation requires a long time. appear.

[Polyimide copolymer precursor solution]
[A. solvent]
The solvent used for the polyimide copolymer precursor solution of the present invention may be any solvent as long as the polyimide copolymer precursor is dissolved therein. Preferably, it is a solvent represented by the formula (2) used to obtain the polyimide copolymer precursor.

  The polymerization solvent and the solvent of the solution may be the same or different, but are usually preferably the same for the production of the solution of the present invention. Moreover, the said solvent may be used individually by 1 type similarly to the said polymerization solvent, or may be used in combination of 2 or more type.

[B. Production of solution]
The amount of the solvent used in the polyimide copolymer precursor solution of the present invention is 5 to 40% by weight of the polyimide copolymer precursor with respect to the total of the polyimide copolymer precursor and the solvent. More preferably, the amount is 10 to 30% by weight.

The solution of the polyimide copolymer of the present invention can be obtained by a known method without particular limitation. Specifically, the following methods are mentioned.
1) A method in which a solution obtained by producing a polyimide copolymer precursor is used as it is.
2) A method in which after the polymerization reaction, a polyimide copolymer precursor obtained by removing with a poor solvent or by desolvation is obtained once and then mixed with the solvent.

  In these methods, there is no limitation on the temperature and the time for dissolution, and normal pressure is sufficient as the pressure. A homogeneous solution in which a polyimide copolymer precursor is dissolved is most preferable, but a non-uniform solution such as a suspension may be used.

[Polyimide copolymer]
[A. Structure and composition]
The polyimide copolymer of this invention has each repeating structural unit represented by said Formula (4a) and (4b) obtained by dehydrating imidating the precursor of the said polyimide copolymer. In the formula, m and n represent a copolymerization ratio (mol%), and m + n = 100 mol%, 70 ≦ m <100, 30 ≧ n> 0. n is preferably 10 to 20 mol%, more preferably 20 mol%.

  When the polyimide copolymer of the present invention is applied to a photosensitive coverlay, when m is 100 mol%, the polyimide film does not have sufficient fold resistance, so that there is a problem in practicality. Moreover, when it is 70 mol% or less, the precursor imparting photosensitivity has a problem that the light transmittance in the ultraviolet region is insufficient. Therefore, when m is 70 ≦ m <100, it is preferable from the viewpoints of fracture resistance and transmittance.

[B. Method for producing polyimide copolymer]
The polyimide copolymer of the present invention can be obtained by dehydrating imidation of the polyimide copolymer precursor by a known method. It can also be obtained by desolvating the polyimide precursor solution of the present invention and simultaneously dehydrating and imidating the polyimide copolymer precursor contained in the solution.

  Dehydration imidization methods can be broadly classified into chemical imidization methods and thermal imidization methods, and all dehydration imidization methods can be applied including methods using both of them.

  In the chemical imidization method, the polyimide copolymer precursor obtained by the above method or the solution is reacted with a dehydrating agent having hydrolysis performance to perform chemical dehydration. The dehydrating agents used are acetic anhydride, aliphatic carboxylic anhydrides represented by trifluoroacetic anhydride, polyphosphoric acid, phosphoric acid derivatives represented by phosphorus pentoxide or mixed acid anhydrides of these acids, methane chloride Examples thereof include acid chlorides represented by sulfonic acid, phosphorus pentachloride and thionyl chloride. These dehydrating agents may be used alone or in combination of two or more. The amount of the dehydrating agent used is preferably 2 to 10 mole ratio with respect to 1 mole of all the diamines used. More preferred is a 2.1 to 4 molar ratio.

  The chemical imidization method can also be carried out in the presence of a base catalyst. The base catalyst used can also use the amine solvent (D) as a base catalyst. In addition to these, organic bases such as imidazole, N, N-dimethylaniline, N, N-diethylaniline, and inorganic bases represented by potassium hydroxide, sodium hydroxide, sodium carbonate, and sodium bicarbonate can be used. The amount of these catalysts used is preferably 0.001 to 0.5 molar ratio with respect to 1 mol of the total amount of all diamines used. More preferably, the molar ratio is 0.05 to 0.2.

  The reaction temperature, reaction time, and reaction pressure for chemical imidation are not particularly limited, and known conditions can be applied. That is, the reaction temperature is preferably from −10 ° C. to around 120 ° C., more preferably from about room temperature to around 70 ° C., and room temperature is practical in practice. The reaction time varies depending on the type of solvent used and other reaction conditions, but is preferably about 1 to 24 hours. More preferably, it is about 2 to 10 hours. A normal pressure is sufficient as the reaction pressure. As the atmosphere, air, nitrogen, helium, neon, argon or the like is used, and there is no particular limitation. However, nitrogen or argon which is an inert gas is preferably selected.

  The thermal imidization method can be carried out by the polyimide copolymer obtained by the above method or a method of thermally dehydrating the solution by heating. A polyimide copolymer or a state in which the solution is dissolved in a solvent, a dispersed suspension, and a polyimide copolymer precursor powder or granule solid isolated from the solution or suspension; Any form may be sufficient. In addition, when the solution or suspension is heated, the solvent used may be refluxed even if the solvent used is evaporated and removed with a dehydrating imidization reaction. The former is best applied to film production and the like, and the latter is suitable for dehydrating imidization reaction in a reactor.

  The thermal imidization method can also be carried out in the presence of a base catalyst, similar to the chemical imidization method. The base catalyst used and the amount used thereof are the same as described in the chemical imidization method.

  In order to remove water generated by the dehydration imidation reaction from the system, another solvent can be allowed to coexist. Solvents used here are benzene, toluene, o-xylene, m-xylene, p-xylene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, bromobenzene, o-dibromo. Examples include benzene, m-dibromobenzene, p-dibromobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-bromotoluene, m-bromotoluene, and p-bromotoluene. These solvents may be used alone or in combination of two or more. When mixed and used, it is not always necessary to select a combination of solvents that are mutually soluble in an arbitrary ratio, and they may be mixed or non-uniform. There is no limit to the amount of these dehydrating agents used.

  There are no particular limitations on the reaction temperature, reaction time, and reaction pressure for thermal imidization, and known conditions can be applied. That is, the reaction temperature can be about 80 ° C. to about 400 ° C., preferably about 100 ° C. to about 300 ° C., and practically about 150 ° C. to about 250 ° C. The reaction time varies depending on the type of solvent used and other reaction conditions, but is preferably 0.5 to 24 hours, more preferably about 2 to 10 hours. Further, normal pressure is sufficient as the reaction pressure. The atmosphere is air, nitrogen, helium, neon, or argon, and is not particularly limited. However, nitrogen or argon which is an inert gas is preferably selected.

Examples of the method using the chemical imidization method and the thermal imidization method in combination include the following methods.
B) A method in which heating is performed simultaneously in the implementation of the chemical imidization method.
B) A method in which a dehydrating agent used in chemical imidization is allowed to coexist when performing the thermal imidization method.

[D. Characteristics of polyimide copolymer]
The precursor of the polyimide copolymer of the present invention has structural units represented by the above formulas (1a) and (1b), m and n are m + n = 100, and represent the mol% of the copolymer composition ratio. . n represents 30 ≧ n> 0, more preferably n is 10 to 20 mol%, and most preferably n is 20 mol%.

  In the case of application to a photosensitive cover lay, which is one of flexible circuit materials, the cover lay is used for, for example, a hinge part (folding part) of a mobile phone, so that it is required to have repeated bendability (fold resistance). The For this reason, in the helix fold resistance test, which is one characteristic representing the folding resistance, the coverlay itself needs to have a numerical value of at least 10 times or more, but considering the influence of the photosensitive additive, the matrix When the numerical value is 30 times or less, the polyimide copolymer is not practically tolerable when the photosensitive additive is applied. It is preferable that n is within the above range because the coating film having the above film thickness has good folding resistance.

  Regarding the heat resistance of the polyimide copolymer of the present invention, the glass transition temperature measured by thermomechanical analysis (TMA) is preferably 270 to 350 ° C, preferably 280 to 340 ° C. The 5% thermal mass reduction temperature in the air heating is 400 to 480 ° C, preferably 420 to 470 ° C.

[Positive photosensitive resin composition]
[A. Composition of Composition and (A) Precursor]
The precursor of the polyimide copolymer (A) contained in the positive photosensitive resin composition of the present invention is a precursor of the polyimide copolymer having structural units represented by the formulas (1a) and (1b). And obtained by the production method. After completion of the polymerization reaction, the following (B) photosensitizer and (C) cross-linking agent are added in succession. The addition method, addition conditions such as temperature and pressure are not particularly limited, and known methods and conditions can be employed.

  The positive-type photosensitive resin composition of the present invention comprises (A) 100 parts by weight of a polyimide copolymer precursor, generates acid upon irradiation with actinic rays, and (B) 2 to 5 parts by weight of a photosensitive agent (polyimide copolymer). And (D) aprotic polar amide solvent of the above formula (2), and (C) a crosslinking agent represented by the above formula (5). .

[B. (B) Photosensitive agent]
The photosensitive agent (B) used in the positive photosensitive resin composition of the present invention is a compound (photoacid generator) that generates an acid by actinic rays in the ultraviolet region generally used in positive photosensitive resin compositions. ) Is used. The photosensitive agent (B) used in the present invention is preferably one that decomposes with respect to active ultraviolet rays and generates an acid, and a known photosensitive agent can be used.

  Specific examples of the photosensitive agent (B) used in the present invention include eight compound groups represented by the following groups (6) to (13). These compound groups are more preferable in the present invention, but are not limited to the following structures as long as they decompose by irradiation with active ultraviolet rays and generate an acid efficiently.

  (B) The photosensitive agent may be used alone or in combination of two or more. Moreover, the addition amount is 2-5 weight part with respect to 100 weight part of (A) precursor of a polyimide copolymer. When the addition amount is within the above range, it is preferable because the sensitivity to ultraviolet rays is high and the properties of the coating film are good.

（６）

(6)

（７）

(7)

（８）

(8)

（９）

(9)

（１０）

(10)

（１１）

(11)

（１２）

(12)

（１３）
（ただし、式Ｑは、水素原子または、下式（１４）で示される１価の基である。）

(13)
(However, Formula Q is a hydrogen atom or a monovalent group represented by the following Formula (14).)

（１４）

(14)

[C. (C) Crosslinking agent]
The crosslinking agent (C) comprising the vinyl ether compound represented by the above formula (5) can be easily synthesized as disclosed in known literature (for example, Chem. Mater., Vol. 6, pp. 1854 to 1860). (1994)).

  The central structure of vinyl ether is not particularly limited, and examples thereof include the following compounds. These may be used alone or in combination of two or more.

  The addition amount of the crosslinking agent (C) is 15 to 25 parts by weight with respect to 100 parts by weight of the polyimide copolymer precursor. It is preferable for the amount added to be in the above range since the properties of the coating film are good.

（１５）

(15)

[D. (D) Solvent]
As the solvent (D) in the positive photosensitive resin composition of the present invention, any solvent can be used as long as the positive photosensitive resin composition is soluble, but the above (A) polyimide copolymer is preferable. The polymerization solvent used to obtain the precursor of The polymerization solvent and the solvent of the solution may be the same or different, but are usually preferably the same for the production of the solution of the present invention. Moreover, the said solvent may be used individually by 1 type similarly to the said polymerization solvent, or may be used in combination of 2 or more type. Furthermore, like the polymerization solvent, the solvent can be used by mixing other solvents within a range not impairing the object of the present invention, and specifically the same as described above.

  The amount of the solvent used in the positive photosensitive resin composition of the present invention is 150 to 1900 parts by weight. It is preferable for the amount added to be in the above range since the properties of the coating film are good.

[E. Other ingredients]
The positive photosensitive resin composition of the present invention is not limited to the essential components (A) to (D), but any other component depending on the purpose, for example, a sensitizer, a leveling agent, a coupling agent, Monomers other than essential monomers to be used, (A) a polyimide copolymer precursor used in the present invention, or oligomers of polyimide and other oligomers, stabilizers, wetting agents, pigments, dyes, and the like may be contained. Absent.

[F. Production method]
The positive photosensitive resin composition of the present invention can be obtained by a known method without particular limitation, and specific examples include the following four.
1) A method obtained by adding (A) a polyimide precursor, (B) a photosensitizing agent, and (C) a cross-linking agent once isolated to the solvent (D). In these methods, the order of addition, the temperature at the time of addition, and the time for dissolution are not particularly limited.
2) A method in which (B) a photosensitive agent and (C) a crosslinking agent are added to a solution containing (A) a polyimide precursor and (D) a solvent obtained by production of a polyimide precursor.
3) A method obtained by performing polymerization after adding (B) a photosensitizer and (C) a crosslinking agent to the solvent (D) in advance.
4) Either (B) a photosensitizer or (C) a crosslinking agent is added to the solvent (D) in advance, followed by polymerization, and then (B) the photosensitizer or ( C) A method of adding a crosslinking agent.

  Conventionally known production conditions can be used for the solution of the positive photosensitive resin composition of the present invention, with no particular limitations on temperature, time, concentration, and pressure.

[G. Use of positive photosensitive resin composition and characteristics of polyimide copolymer]
The polyimide copolymer of the present invention has structural units represented by the above formulas (4a) and (4b), and m and n are m + n = 100, and represent mol% of the copolymer composition ratio. The polyimide copolymer of the present invention can be obtained by desolvating the positive photosensitive resin composition of the present invention and simultaneously dehydrating and imidating the (A) polyimide precursor contained in the solution.

  In the method, the reaction temperature, reaction time, and reaction pressure are not particularly limited, and known conditions can be applied, and the reaction can be performed in the same manner as in the imidation of the polyimide copolymer precursor.

  In the polyimide copolymer of the present invention represented by the above formulas (4a) and (4b), n represents 30 ≧ n> 0, more preferably n is 10 to 20 mol%, and most preferably n. Is 20 mol%. In the case of application to a photosensitive cover lay, which is one of flexible circuit materials, the cover lay is used for, for example, a hinge part (folding part) of a mobile phone, so that it is required to have repeated bendability (fold resistance). The For this reason, there is a problem that the cover lay itself, which is one characteristic representing folding resistance, cannot be practically tolerated if the numerical value does not have at least 10 times. It is preferable that n is within the above range because the coating film having the above film thickness has good folding resistance.

[Pattern formation method]
[A. Forming method]
The positive pattern forming method of the present invention comprises a step (I) of coating the positive photosensitive resin composition of the present invention on a substrate, and drying the substrate coated with the resin composition at 50 to 160 ° C. The step (II), the step (III) through which the obtained coating film is exposed to active ultraviolet rays through a mask pattern and then heated at 80 to 200 ° C., and an aqueous solution of an alkali metal carbonate, Step (IV) for developing the positive pattern by dissolving only the exposed part of the coating film, and heat-treating the developed positive pattern, thereby having structural units represented by the above formulas (4a) and (4b) And (V) forming a positive pattern containing a polyimide copolymer.

  First, the resin composition is coated on a wafer using a spin coater, and then the coating film is dried at 50 to 160 ° C., preferably 70 to 140 ° C. The obtained coating film is transmitted through a mask on which a pattern is drawn and irradiated with active ultraviolet rays of 365 nm.

  Next, the coating film is heated again at 110 to 200 ° C., preferably 120 to 180 ° C., and then the coating film is irradiated with actinic rays using an aqueous solution of an alkali metal salt carbonate such as sodium carbonate or potassium carbonate. Only the part is dissolved and developed, and rinsed with pure water. The alkali metal carbonate is preferably sodium carbonate because it is inexpensive.

  As a developing method, methods such as spraying, paddle, dipping, and ultrasonic waves can be used. Thereby, a desired positive pattern can be obtained on the target wafer.

  Furthermore, the resin composition can be cured by heat-treating the coating film at 180 ° C. for 2 hours and at 250 ° C. for 2 hours to form a polyimide film having excellent film characteristics. Also, the intermediate insulating layer of the multilayer printed wiring board can be formed by a similar method.

[B. Photosensitive mechanism]
In the positive pattern forming method of the present invention, the resin composition of the present invention is spin-coated on a substrate and then dried by heating. At this time, (A) the carboxyl group of the precursor of the polyimide copolymer and (C) the vinyl ether moiety of the cross-linking agent form a hemiacetal bond, thereby forming a cross-linked structure. Next, by irradiating actinic rays such as ultraviolet rays and heating, in the actinic ray exposure part, (B) the photosensitizer is decomposed, acid is generated and diffused, and the hemiacetal bond is cleaved to form a carboxyl group. Will play. The carboxyl group of this polymer has moderate solubility in an alkaline aqueous solution. As a result, only the portion irradiated with actinic rays such as ultraviolet rays exhibits high solubility in the alkaline aqueous solution, and the unirradiated portion is insoluble. Therefore, it does not dissolve. By using this concept of chemical amplification type, the amount of additives other than resin can be reduced, and a highly sensitive positive pattern can be formed.

[Usage]
The positive photosensitive resin composition of the present invention containing the precursor (A) of the polyimide copolymer (A) of the present invention can be developed with an aqueous solution of an alkali metal carbonate and has a high ultraviolet light region. Since it has transmittance and is excellent in photosensitivity, a fine pattern can be formed. For this reason, it is suitably used as a circuit material, a flexible printed board, and a coverlay. Furthermore, unlike the conventional materials, these polyimide copolymer layers or polyimide copolymer films have excellent heat resistance and transmittance in the ultraviolet light region, and have folding resistance, insulation, and flame retardancy. Have both.

  The cover lay of the present invention is formed using the above-described polyimide copolymer precursor of the present invention, a polyimide copolymer precursor solution, a polyimide copolymer, and a positive photosensitive resin composition. When a positive photosensitive resin composition is used, in order to produce a coverlay on a flexible printed circuit board, a positive pattern is developed in the same manner as the pattern forming method of the present invention, and the developed positive mold By subjecting the pattern to a heat treatment in a nitrogen atmosphere at 50 to 250 ° C. for 2 hours and further at 250 ° C. for 2 hours, for example, the resin composition can be cured and a polyimide layer having excellent film characteristics can be formed. In the curing conditions, the above examples are not limited, and the curing temperature is preferably 100 to 300 ° C, more preferably 150 to 250 ° C, and most preferably 180 to 220 ° C. The curing time is the same, preferably 0.5 to 12 hours, more preferably 1 to 6 hours, particularly preferably 1 to 3 hours, and most preferably 1.5 to 2 hours.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited at all by these Examples. Each physical property was measured by the following method.
(1) Logarithmic viscosity; measured in an N, N-dimethylacetamide (DMAc) solution at 35 ° C.
(2) E-type mechanical viscosity: measured using a rotor No. 4 at 25 ° C. using an E-type measuring device TVH-22H manufactured by Toki Sangyo Co., Ltd.
(3) Glass transition temperature (Tg): measured using a thermomechanical analysis TMA-50 manufactured by Shimadzu Corporation at a heating rate of 10 ° C./min.
(4) Light transmittance: Measured using Multi-spec-1500 manufactured by Shimadzu Corporation.
(5) Solder heat resistance test: A test piece having a protective film formed on a copper foil was prepared on the molten solder liquid surface maintained at 255 to 265 ° C., and floated for 5 seconds with the protective film surface facing upward. The presence or absence of blistering was confirmed visually.
(6) Folding resistance test: Folded 180 ° with a double-sided plate and applied a load of 5 kg to the bent part. This was repeated, and the number of occurrences of peeling of the bent portion was measured by observing the bent portion with an optical microscope.
(7) Migration resistance test: A protective film with a thickness of 25 μm is formed on a polyimide substrate with copper wiring (9 μm thickness) of line / space = 30/30 μm, and 5.5 VDC at 85 ° C. and 85% RH. It was energized for 1000 hours and the presence or absence of a short circuit due to insulation deterioration was confirmed.
(8) Flame retardancy test: A protective film with a thickness of 15 μm is formed on a circuit substrate consisting of two layers of 12 μm copper layer / 25 μm polyimide layer, and conforms to the thin material vertical combustion test of the UL method (subject 94). Measured.

[Example A]
A vessel equipped with a stirrer, a nitrogen inlet tube, and a thermometer was charged with 218.12 g (1.00 mol) of pyromellitic dianhydride (hereinafter PMDA) and 600 g of N, N-dimethylacetamide (hereinafter DMAc), and nitrogen. Stir at room temperature under atmosphere. Next, 107.98 g (0.7 mol) of diaminomethyl-bicyclo [2.2.1] heptane (hereinafter referred to as NBDA) and 60.07 g (0.3 mol) of 4,4′-diaminodiphenyl ether (hereinafter referred to as ODA) (NBDA / (ODA ratio: 80/20 mol% / mol%) was dissolved in 300 g of DMAc, and was added dropwise while paying attention to an increase in temperature. Then, it was made to react at room temperature for about 15 hours, and the solution of the precursor of a polyimide copolymer was obtained.

  This polyimide copolymer precursor had a logarithmic viscosity of 0.70 dl / g and an E-type mechanical viscosity of 82700 mPa · sec (measurement temperature 25 ° C.). The transmittance of the polyamic acid film with a thickness of 20 μm at 365 nm was 10%.

  The polyimide copolymer precursor solution was cast on a glass plate using a bar coater to obtain a 20 μm polyimide copolymer film. When the fracture resistance test of this polyimide copolymer film was conducted, no cracks were observed even after repeated 30 times.

[Examples B to E and Comparative Examples A to C]
Example A was the same as Example A except that the ratio of NBDA to ODA (mol% / mol%) and the solvent were changed as shown in Table 1. The results are shown in Table 1.

[Example 1]
Using the polyimide copolymer precursor solution obtained in Example A as it is, 0.9 g of a photosensitizer represented by the following formula (16) with respect to 100 g of the solution (with respect to the polyimide copolymer precursor). 3 parts by weight) and 4.5 g of a crosslinking agent represented by the following formula (17) (15 parts by weight with respect to the precursor of the polyimide copolymer) were added. The solution was filtered using a Teflon (registered trademark) filter to obtain a positive photosensitive resin composition solution.

（１６）

(16)

（１７）

(17)

The obtained solution was coated on a 4-inch silicon wafer by a spin coater and dried in a drying oven at 80 ° C. for 10 minutes to obtain a 16 μm coating film. Half of this coating film was covered with a Kapton film that did not allow UV light to pass through, irradiated with an energy of 300 mJ / cm ² by a broadband UV light exposure machine, and then continuously heated at 100 ° C. for 5 minutes. Next, paddle development was performed for 60 seconds with a 1% aqueous sodium carbonate solution, followed by washing with pure water. After this development and washing, the coating film on the unirradiated part was not changed, but the irradiated part was dissolved and washed, there was no residue, and the difference between the irradiated part and the unirradiated part was clear.

  Next, a positive type relief pattern creation test, a solder heat resistance test, a crease resistance test, a migration resistance test, and a flame resistance test were performed.

  In the positive type relief pattern creation test, the silicon wafer was replaced with 1 ounce rolled copper foil, and the same evaluation was performed using a test pattern instead of Kapton Film (trademark). As a result, a positive relief pattern in which only the ultraviolet irradiation part was dissolved could be obtained. When the obtained pattern was observed with an optical microscope, it was confirmed that a pattern having a film thickness of 10 μm and a line width of up to 30 μm was formed. Furthermore, this pattern was heated from room temperature to 250 ° C. for 2 hours under a nitrogen stream, and baked at 250 ° C. for 2 hours to complete the polyimide formation of the coating film. The obtained polyimide film maintained good pattern formability.

  The solder heat resistance test, the crease resistance test, and the flame resistance test were applied on a 1 ounce rolled copper foil glossy surface, and the migration resistance test was applied on a migration resistance evaluation substrate. Subsequently, 1% sodium carbonate aqueous solution was spray-developed at a pressure of 0.15 Pa for 60 seconds, followed by washing with water and drying. Then, it imidated from room temperature to 250 degreeC for 2 hours and 250 degreeC for 2 hours, and obtained the polyimide coating film.

  As the evaluation of the obtained polyimide coating film, no abnormality was observed in the appearance after the solder heat resistance test and after the 20-fold resistance test. Further, in the migration resistance test, no defect was observed within 1000 hours, and no abnormal appearance of the test piece after the test was observed. The result of the flame retardancy test was an evaluation of VTM-0. The results are shown in Table 2.

[Examples 2 to 5 and Comparative Examples 1 to 3]
A positive photosensitivity was obtained in the same manner as in Example 1, except that the precursors of the polyimide copolymers obtained in Examples B to E and Comparative Examples A to C were used with a crosslinking agent and a photosensitizer as in Example 1. A solution of the functional resin composition was obtained. Moreover, it evaluated similarly to Example 1. FIG. The results are shown in Table 2.

[Reference Examples A to C]
In Comparative Example A, a polyimide polymer precursor was obtained in the same manner as Comparative Example A, except that the solvent shown in Table 3 was used and polymerization was performed without using ODA. Moreover, it evaluated similarly to the comparative example A. The results are shown in Table 3.

  The present invention relates to a precursor of a polyimide copolymer, a solution of the precursor obtained therefrom or a positive photosensitive resin composition, and a polyimide copolymer obtained from the precursor, the solution, or the resin composition. Can be given.

  The resin composition can be developed with an aqueous solution of a low-concentration alkali metal carbonate having a low environmental load, and has a high transmittance in the ultraviolet light region, so that a fine pattern can be formed, and there is a possibility of giving a load to the environment. Free of high halogen containing compounds and antimony compounds.

  The polyimide copolymer has excellent electrical properties while having good fracture resistance, and has both heat resistance, insulating properties, and flame retardancy.

  Therefore, the present invention can provide a coverlay having a good folding resistance and a flexible printed circuit board using the coverlay. In addition, by using the resin composition of the present invention and the like and the positive pattern forming method of the present invention, a circuit material having excellent chemical resistance, electrical characteristics and the like can be obtained.

  Furthermore, the cover lay of the present invention is flexible for use in not only computer-related devices such as personal computers and printers, information-related devices typified by mobile phones, and AV devices such as televisions and DVD players, but also any electric / electronic device. It can be suitably used as a printed circuit board or circuit material.

Claims (17)

A polyimide copolymer precursor comprising the repeating structural units represented by formulas (1a) and (1b).

(In the formula, m and n represent a copolymerization ratio (mol%), and m + n = 100 mol%, 70 ≦ m <100, 30 ≧ n> 0.) The precursor of the polyimide copolymer according to claim 1, wherein norbornanediamine represented by formula (3), 4,4′-diaminodiphenyl ether, and pyromellitic dianhydride are represented by formula (2): The polyimide copolymer precursor according to claim 1, which is obtained by reacting in an aprotic polar amide solvent represented.

(Wherein _R 1 to R ₃ is an alkyl group having 1 to 3 carbon atoms, it may be the same or different from each other.)

(3) The precursor of a polyimide copolymer according to claim 2, wherein the aprotic polar amide solvent of the formula (2) is N, N-dimethylacetamide. The polyimide copolymer precursor according to any one of claims 1 to 3, wherein the copolymerization ratio n of the formula (1b) is 10 to 20 mol%. The polyimide copolymer precursor according to any one of claims 1 to 4, wherein a film obtained from the precursor has a transmittance at 365 nm at a film thickness of 10 µm of 10% or more. A precursor of the polyimide copolymer according to claim 1. A polyimide copolymer precursor solution comprising the polyimide copolymer precursor according to any one of claims 1 to 5 and the aprotic polar amide solvent of the formula (2). The polyimide copolymer which has each repeating structural unit represented by Formula (4a) and (4b) obtained by dehydrating imidating the precursor of the polyimide copolymer in any one of Claims 1-5.

(Wherein, m and n are the same as above). The polyimide copolymer precursor solution according to claim 6 is desolvated, and at the same time, the polyimide copolymer precursor represented by the formulas (1a) and (1b) contained in the solution is dehydrated imide. A polyimide copolymer represented by the above formulas (4a) and (4b), which is obtained by conversion. The polyimide copolymer according to any one of claims 7 and 8, wherein the fracture resistance test value is at least 30 times. A positive photosensitive resin composition containing the following (A) to (D):
(A) 100 parts by weight of a precursor of a polyimide copolymer having each repeating structural unit represented by the above formulas (1a) and (1b) (based on the following parts by weight)
(B) 2 to 5 parts by weight of a photosensitizer that generates an acid upon irradiation with actinic rays (C) 15 to 25 parts by weight of a crosslinking agent represented by the general formula (5) (D) aprotic compound of the above formula (2) 150-1900 parts by weight of polar amide solvent

(In the formula, l represents an integer of 1 or more, and R represents a monovalent or higher aromatic group or aliphatic group.) The polyimide copolymer which has each repeating structural unit represented by said Formula (1a) and (1b) contained in a photosensitive resin composition simultaneously with desolventization of the photosensitive resin composition of Claim 10 A polyimide copolymer represented by the above formulas (4a) and (4b), which is obtained by dehydrating and imidating the precursor. The polyimide copolymer according to claim 11, wherein the fracture resistance test value is at least 10 times. A step (I) of coating the positive photosensitive resin composition according to claim 10 on a substrate, a coating step (II) for drying the substrate coated with the solution at 50 to 160 ° C, The obtained coating film is exposed to active ultraviolet rays through a mask pattern, and then heated at 80 to 250 ° C., using an aqueous solution of an alkali metal carbonate, and only the exposed portion of the coating film. Step (IV) of developing a positive pattern by dissolving and heat-treating the developed positive pattern to contain a precursor of a polyimide copolymer represented by the above formulas (1a) and (1b) And a step (V) of forming a positive pattern. The positive pattern forming method according to claim 13, wherein the aqueous solution of alkali metal carbonate according to claim 13 is an aqueous sodium carbonate solution. A circuit material obtained by the positive pattern forming method according to claim 13. The polyimide copolymer precursor according to any one of claims 1 to 5, the solution of the polyimide copolymer precursor according to claim 6, and the polyimide copolymer according to any one of claims 7 to 9. A cover lay formed using any one of the positive photosensitive resin composition according to claim 10 or the polyimide copolymer according to any one of claims 11 to 12. A flexible printed board using the coverlay according to claim 16.